Elevator control system



0a. 10, 1933. W. F. EAMES ELEVATOR CONTROL SYSTEM Original Filed April5, 1928 INVENTOR lA/ZY/l'd/H FEames.

WITNESSES:

A TO EY Patented Oct 10, 1933 William F. Eames, Edgewood, Pa., assignorto Westinghouse Electric & .Manufacturing Com- Q pany, a corporation ofPennsylvania Original application Aprils, 1928, Serial No..

267,711. Divided and this application Septemher 2, 1931. Serial No.560,694 a .5 Claims. (cum-223 This application is a division ofmyapplication Serial 267,711, filed April 5, 1928.

My invention relates to motor-controlsystems and has particularrelation. to elevators, hoists and similar machinery.

An object of my invention is to provide a control system for motorswherein a motor may be accurately stopped at anypredetermined point initstravel, 1

Another object of my invention is to provide a control system for anelevator motor wherein the elevatormay be stopped accurately level withthefloor without overrunning or underrunning the floor.

Another object of my invention is to provide a control system forelevators of the Ward- Leonard type wherein the generator structure ismodified to insure accurate speed regulation of the motor at low speeds,independent of loading conditions.

Another object of my invention is to provide a system, as described inthe preceding paragraph, wherein the cojmmutating poles of a generatormay be so arranged as to achieve an effect of cumulatively compoundingthe generator atsuch times as the generator is operating atlow voltagesand low currents.

In elevator systems controlled by means of variable-voltage equipmentfor use in modern installations, it is desirable that the elevator speedshall be regulated within comparatively narrow limits, independent ofthe load upon the elevator, since, in high-speed-elevator work, theaccuracy of landing is primarily based upon accuracy of speedregulation,that is, thenormal speed of the elevator should be the same, regardlessof the load thereon, when operating under predetermined conditions ofcontrol.

To accomplish this result, the Ward-Leonard or variable voltage systemof control has been devised wherein variations in the speed of the motorwhich would normallyoccur with variations in the load upon the elevatorare compensated for by means of cumulatively compounding the generatorto produce such rising voltage characteristic on the generator as willcompensate for the drooping speed characteristic of the motor. .The useof; cumulative compounding of the generator substantially accomplishesthis result within rather wide ranges of load. My invention will bedescribed with reference to theaccompanying drawing, wherein,

Figure 1 is a diagrammatic view of an elevatorcontrol system of theWard-Leonard type.

Fig. 2 is a diagrammatic view of thegenerator showing the arrangement ofmain-poles andcommutating poles, a portion of which view is in sec--tion, and I Fig. 3 is a diagrammatic view of a voltage curve obtained bythe use of the generator hereinafter 0 described.

Referring "to the drawing, Ihave illustrated, inFig. 1, an elevator carCsupported upon a suitable cable Ca which passes overv a hoist drum D toa suitable counterweight Cw. Thehoisting drum D is illustrated asdirectly coupled to the armature EM of a hoisting motor EM, the fieldwinding EMF of whichis connected for excitation by a suitable source ofenergy designated by conductor L1 and L2. The armature EM of the motorEM is connected in loop circuit with the armature G of a generator G.-The generator G is provided with a separately excited field winding GF aseriesfield winding GSF, a demagnetizing winding GAF, and a commutatingpole winding GC. The generator G is driven by means of asuitable motorM, illustrated as of the shunt-wound type having its armature M and itsshunt field windin MF connected across line conductors L1 and L2.

" Thecontrol of the direction andspeed of the elevator car Ca isillustrated as of the usual type whereinup and down-direction switches 1and 2, respectively, actuated by means of a' car-' switch Cs, controlthe direction of current supplied to the separately excited fieldwinding GF .5 of the generator G, while a speed switch 3, controlled bythe car switch Cs, is. arranged to control the value of thecurrentsupplied to the field winding GF.

Referring to Fig. 2, the generator G is illus- 0 trated diagrammaticallyas of the four-pole type, wherein the main poles are designated by thereference characters 5, 6,17 and 8, respectively. Suitably locatedbetween the main poles 5, 6, etc.,

I have illustrated commutating or interpoles 9,, 10, 11 and 12, it beingunderstood thatthe number of inter poles corresponds to the number ofmain poles provided on the generator G. As

is the usual practice in generators of this type, each of the interpoles is provided with a wind- 9 ing (one of which is designated by thecharacter 13) suitably connected in series relation with eachother andwith the armature. G.

, :Each of the inter poles 9, 10, etc. may be provided witha core 14suitably secured to the frame 15 of the generator G by means of abolt16. The core structure 14 and bolt 16, as well asthe frame structure 15,are all constructed of suitable magnetizable material. Interposedbetweenthe core member 14 and the frame 15, is a shim or Washer 17 constructedof non-magnetizable material, for example, copper, brass or fiber. As iswell known, the interposition of a section of non-magnetizable materialbetween the frame 15 and the core member 14 constitutes the equivalentof an air gap between these members. Hence, a portion of the magneticpath through the inter pole 9 is constituted with a relatively smallcross sectional area of low reluctance and a relatively large section ofhigh reluctance.

The operation of my system will best be understood from an assumedoperation of the elevator car C. Assuming that it is desired to move thecar C upwardly, the car switch Cs may be moved in a counter-clockwisedirection to energize up-direction switch 1 by means of a circuit whichextends from line conductor L1 through conductors 20 and 21, contactmembers 22, 23 and 24 on car switch Cs, conductor 25, the coil ofup-direction switch 1, conductors 26, 27, contact members 37"of aninductor relay 37, and conductors 39 and to line-conductor L2.Updirection switch 1, when actuated, supplies current in one directionto the generator-field winding GF by way of a circuit which extends fromline conductor Ll through conductors 29, contact members a ofup-direction switch 1, conductor 30, separately excited field windingGF, conductor 31, resistor 32, conductors 33 and 34, contact members bof up-direction switch 1 and conductor 40 to line conductor L2.Generator G now supplies voltage to the armature of elevator motor EM,and the car C starts upwardly. The voltage supplied by generator G willbe dependent upon the value of exciting current in theseparately-excited-field winding GF with the addition of voltage inducedby the cumulative-compounding effect of the series-field winding GSF.The effect of the winding GSF, since it is in series relation with thearmature G and EM of the generator and motor, respectively, will begreater or less dependent upon the load on the elevator car C at anygiven instant. An additional degree of generator compounding, alsodetermined by the load on the elevator, is imposed by the commutatingpoles, as will be described more in detail hereinafter, in connectionwith Fig. 3. Hence, regardless of the load upon the elevator car C, themotor EM will be supplied with sufiicient voltage to insure itsoperating at substantially constant speed for any given value ofexcitation current supplied to the separately-excited-field winding GF.

In the system described and illustrated, the control is of the ordinaryinductor-landing type wherein slow down is automatically initiated andthe car is brought to a stop, without intervention on the part of theoperator, by means of slow-down inductors 35 and 36 for the up and downdirections, respectively, and stopping inductor 37.

When the up-direction switch 1 is actuated to close its contact membersa, a self-holding circuit is completed thereby for maintaining theup-direction switch 1 in its actuated position until stopping inductorrelay 37 opens its contact members 37. This holding circuit extends froma line conductor L1 through conductor 29, contact members a ofup-direction switch 1, conductors 30 and 38, the coil of up-directionswitch 1, conductors 26 and 27, normally-closed contact members 37 ofstopping inductor relay 37, conductors 39 and 40 to line conductor L2.Hence,

. until stopping inductor relay 37 is actuated, the

up-direction switch will remain operative and the car will continue itsupward movement, even though the car switch Cs is centered.

If it is desired to move the car C at a greater speed, the car switch Csmay be moved to the left to its extreme position, supplying energizingcurrent to speed switch 3 by way of a circuit which extends from theline conductor Ll through conductors 20 and 21, contact members 22, 23and 41 on car switch Cs, conductor 42, the coil of speed switch 3 andconductors 43 and 40 to line conductor L2. The actuation of speed switch3 shunts resistor 32 from the field-winding circuit by way of conductors44 and 45, thus increasing the value of excitation current supplied tothe separately-excited-field winding GF. Hence, the elevator motor EMwill accelerate and operate at the speed corresponding to this new valueof field excitation.

When speed switch 3 is actuated, it completes a self-holding circuit foritself, which circuit extends from a line conductor L1 throughconductors 29 and 46, contact members I) of speed switch 3, conductor47, contact members 35' of up slow-down inductor 35, conductor 48,contact members 36 of slow-down inductor relay 36, conductors 49 and 42,the coil of speed switch 3 and conductors 43 and 40 to line conductorL2.

When it is desired to stop the elevator car, the car switch Cs will bereturned to its central or illustrated off position. By reason of theholding circuits for up-direction switch 1 and speed switch 3,previously described, the car will continue its upward motion at highspeed. Centering the car switch Cs, however, closes a circuit forenergizing the actuating coils of inductor relays 35 and 37. Thiscircuit extends from line conductor L1 through conductors 20 and 21,contact members 22, 23 and 50 on car switch Cs, conductor 51, the coilof stopping inductor relay 37, conductor 52, the coil of slowdowninductor relay 35, conductor 53, contact members (1 on up-directionswitch 1 and conductors 54, and 40 to line conductor L2.

As the car approaches the floor at which it is desired to stop, theslow-down inductor relay 35 will be brought adjacent an inductor plate35 (one of which plates is provided at each of the fioors past which theelevator moves) and the inductor relay 35, now energized, is actuated toopen its contact members 35'. Opening contact members 35 releases theholding circuit for speed switch 3, which switch is restored to itsnormal condition, opening its contact members a and reinserting resistor32 in circuit with the separately excited field winding GF to reduce thespeed of the car in correspondence with the value of excitation currentnow supplied to field winding GF.

As the car approaches more closely to the desired floor, stop inductorrelay 37 will be brought adjacent an indicator plate 37 associatedtherewith (one of which also is located adjacent each of the floors pastwhich the car moves) and relay 37 will be caused to open its contactmembers 37' to release the holding circuit for up-direction switch 1.Up-direction switch will, when deenergized, open the circuit for thepartly excited field winding GF, and the car will be brought to a stop.It will be observed that, with the system of control just described, theelevator car C will be decelerated from its normal high speed to alanding speed prior to the final stopping of the car. For acparent thatthe speed of the car at this low matterated is .fixed by the relativepositioning of the inductor plates and 37".

It will be observed that, under the conditions just described, contactmembers c of up-direction, switch 1 will complete a circuit connectingthe demagnetizing-field winding GAF across the terminals of the armatureEM of the elevator motor EM. ,The demagnetizing-wi'nding GAF is so woundand arranged that, when connected across the terminals of the motorarmature EM, the circulating current in the armature EM will excite thewinding GAE to oppose-the efiectof the separately excited and seriesfield windings GF and GSF to thus reduce the voltagev of the generatorto zero and to thereby bring the elevator motor to a stop. It is assumedthat, when the motor EM is brought to a stop, the usual mechanical brake(not shown) will be applied to maintain the car stationary.

Referring to Fig. 3, to illustrate the influence of my invention on agenerator, I have shown characteristic voltage curves of a cumulativelycompounded generator suitable for elevator'applications, in whichgenerator-voltage values are plotted as ordinates, against generatorload values, expressed in percentages of full-load ourrent, asabscissaa. The curves illustrate the variationsin terminal voltage froma negative or overhauling load of approximately full load to full load.The no-load voltage is shown as approximately 15 volts, which, ashereinbefore stated, corresponds to atypical landing speed i of anelevator motor. Curve 56 is typical of a generator provided with normalcompounding means, while curve 5'7 illustrates the improved voltageregulation effected in the practice of my invention.

Referring to curve out which the slope of the curve is substantiallyconstant as the major portioni of the load range, and to that portion ofthe load range throughout which the slope of the curve departs from thedesired or substantially constantvalue as the restricted portion of theload range. Since the. slope of curve 56 throughout the restrictedportion of the load range differs from that throughoutthe major portionof the load range, it will be apparent that a degree of compoundingeffective to produce a desired landing speed of the elevator motorthroughout the major portion of the load range, will be ineffective toproduce the same motor speed throughout the restricted portion thereof.As noted hereinbefore, a small actual variation in. generator voltagethroughout the restricted portion of the. load range, when the elevatormotor is operating at the landing speed, constitutes a considerablepercentage variation. Curve 57 represents a desirable. voltagecharacteristic for a generatoninthat the variations 56, it will beobserved that, throughout the load range from 10% to 100%" in generatorvoltage are substantially proportional to the generator load throughoutthe entire load range. By organizing a generator in accordance withmyinvention, the voltage character- By comparing curves 56 and 57, it willbe seen that the slope of curve 56.may be corrected to conform to thatof curve 57, by subjecting the generator to an additional component ofexcitation, the value of which varies as a function of the generatorload throughout the restricted portion of theload range, and remainssubstantially constant throughout the major portion thereof. The mannerin which the described construction of the commutating poles of thegenerator is eifectiveto produce thisresult may be set forth as follows.

To'provide satisfactory commutating characteristics for the generator,the flux set up by the 'commutating pole windings should besubstantially proportional to load throughout a predetermined range ofload values, and should be of by the current in the armature windings.now, the flux of the commutating pole windings .is' permitted topredominate, to a predetermined degree, over the flux set up by thecurrent in the armature windings, the current in the commutated armaturecoils will beprematurely reduced to zero and reversed. ,Thereversecurrent flowing in the commutated coils, of course, sets up aflux which is of such a direction as to add or subtract, directly to orfromthe flux of the main field windings and thus exerts a compoundingaction on the generator. It follows that this compounding action iscumulative when the load is positive, and differential when the load isnegative, since thecommutating pole windings carry the load current.

As described hereinbefore, this additional component of generatorexcitation should be proportional to load throughout the restrictedportion of the load range, and should remain constant throughout theremainder thereof. In other words, the rate of increase ofcommutating-pole flux should be greater throughout the restrictedportion of the load range than throughout the remainder thereof.

Referring again to the construction of the commutating poles, ,it willbeobserved that the magnetic circuit for the flux of the windingsthereof comprises a main pole core, a connecting bolt, and anon-magnetic spacer. When both the pole core and bolt are unsaturated,it is apparent that a given increase in load current will produce agiven increase in commutating-pole flux. If, now, the bolt is permittedto saturate at a predetermined value of load, it follows that subsequentincreases in load will produce smaller increases in commutating-poleflux. In accordance with my invention, I permit the bolt to saturate atthe point atwhich the slope of curve 56 assumes the desired value.

, It will be seen, therefore, that, throughout the restricted portion ofthe load range, the commutating pole flux increases as such a functionof the load as to perform not only its normal function, but to supply anadditional component of main generator excitation in proportion to theload; that, throughout the major portion of the load range, by-reason ofthesaturated condition of a portion of its magnetic circuit, the flux ofthe commutating poles increases less rapidly, or,

i io

increases as such a function of theload that the additional component ofgenerator excitation supplied thereby remains substantially constant. Inaccordance with my invention, therefore, when the load is, positive ornegative, the generator voltage corresponding to a particular load isincreased or decreased to such an extent as to cause the actual voltagecharacteristic of the generator to assume a substantially constant slopethroughout the entire load range.

It will, therefore, be observed that, by utilization of the structurejust described, the inaccuracy of speed regulation at low speeds iscorrected without disturbing the speed regulation normally imposed bythe compounding of the generator G by means of the series field windingGSF.

In actual practice, it has been observed that the arrangement justdescribed achieves an effect of correcting the inaccuracy of speedregulation to the extent of at least 50% andthis amount of correction isreadily appreciated when the con-. trol system herein described isapplied to elevators having a device for automatically stopping theelevator car level with the floor, such as that herein described andalso described in the copending application of E. M. Bouton, Serial No.731,921, filed August 14, 1924, and assigned to the WestinghouseElectric and Manufacturing Company. With such automatic landingequipment, initiation of slow down at a definite distance from thefloor, regardless of the load on the elevator, causes the car to stopsubstantially level with the fioor without further attention on the partof the attendant. In actual test, such systerns stop the car level withthe floor within a half inch, regardless of load. However, by the use ofthe system for providing additional com-' pounding of the generator, asherein described, such inaccuracy can be reduced to less than onefourthof an inch.

Another method of accomplishing the result of effecting an equivalent ofadvancing the commutating plane is illustrated in Fig. 2 wherein thecore 14 of the commutating pole is spaced from the frame 15 by a pair oflugs 60, formed integrally with the pole core 14 or introduced asspacers. This construction provides an air gap 61, and the pole operatesin the same manner as described for the core 14. In this case, however,the bolt 16 should be constructed of non-magnetizable material.

In the present application, I do not claim a control system arranged toaccommodate a generator organized in accordance with the presentinvention, since this subject-matter is claimed in my application,Serial No. 267,711, filed April 5, 1928, hereinbefore identified.

My invention may be practiced in many ways, the embodiments hereindescribed are illustrative only, and I do not desire to be limited toany of the details shown or described therein except insofar as definedin the appended claims.

I claim as my invention:

1. In a generator for supplying a variable load, said generator having afixed zone of commutation, means for exciting said generator, meansincluding commutating poles and magnetizing windings therefor disposedto supply one componentof fiux for commutating purposes, and to supplyanother component of flux to vary the voltage of said generator inaccordance with the value of said load, and means responsive to saidlead to limit the cumulative effect of said windings on the voltages ofsaid generator to a restricted range of load values.

2'. In a generator for supplying a variable load, said generator havinga fixed zone of commutation, means for exciting said generator,commutating. poles and magnetic circuits associated therewith,magnetizable windings on said poles disposed to supply one component offlux for commutating purposes, and an additional component of flux tovary the voltage of said generator, and means responsive to the load onsaid generator to render said commutating pole windings effective tovary said generator voltage in accordance with said load throughout apredetermined range of load values.

3. In a generator for supplying a variable load, said generator having afixed zone of commutation, means for exciting said generator,commutating poles and magnetic circuits associated therewith,magnetizable windings on said poles disposed to supply one component offlux for commutating purposes, and means disposed in the magneticcircuits of the flux of said commutating poles to render saidcommutating pole windings effective to vary said generator voltage inaccordance with said load throughout a predetermined range of loadvalues.

4. In a generator for supplying a variable load, said generator having afixed zone of commutation, means for exciting said generator to causesaid generator to develop a voltage, means comprising commutating polewindings to cause said generator to develop an additional component ofvoltage proportional to said load, and means for limiting the effect ofsaid last named means to a predetermined range of load values.

5. In a generator for supplying a variable load, said generator having afixed zone of commutation, a first means for exciting said generator tocause said generator to develop a voltage, a second means for causingsaid generator to develop an additional component of voltageproportional to said load, said second means comprising commutating polewindings and means to define a magnetic circuit for the flux thereof,and means disposed to control the reluctance of said circuit to limitthe efiect of said second means to a predetermined range of load values.

WILLIAM F. EAMES.

